The subject matter herein relates generally to terminal crimping machines for crimping electrical terminals to a wire.
Terminal crimping machines have long been used in the connector industry to effect high-speed mass termination of various cables. It is common practice for the terminal crimping machine to have an applicator that holds crimp tooling, such as an anvil and a movable ram, and a driving actuator that moves the ram relative to the anvil during a crimping stroke to crimp a terminal or connector to an end of a wire.
However, crimped electrical connections may have degraded electrical performance, such as from high electrical resistance at the terminal/wire interface or between strands of the wire. For example, surface oxide that forms on the outer surface of the wires, such as on aluminum wires, presents problems in the crimped termination. The oxide film is an electrical insulator and is difficult to displace during crimping, particularly on inner strands of the wire that do not engage the crimp barrel of the terminal. Many of the strands within the crimped wire bundle can be electrically isolated from the termination, which can result in higher than expected crimp resistance, less stable crimp resistance, and the potential for excess heating of the termination.
Some known terminals use high pressure contact points such as serrations or indentations along the crimp barrel to increase wire deformation and enhance the displacement of the oxide film that contacts the crimp barrel. However, such serrations only affect the outer strands and have no effect on the oxide films on the inner strands. Also, the high pressure features can be difficult to produce and can require high crimping effort. Other known terminals use of additives such as brass powder or brass screens that puncture the oxide and form intermetallic bridges between strands. However, the additives increase cost and process complexity and can serve as contaminants to adjacent processes.
A need remains for a crimped terminal having low resistance at the crimped terminal/wire interface and between the strands of the wire.